1. Field of the Invention
This invention relates to a vibrating machine of the type in which vibratory motion and periodic directional force resultants are developed by the use of eccentric masses concurrently rotated about parallel axes in opposite directions. The direction of the acting force resultants is selectively varied by means of a shifting coupling which is used to change the angular phase relationship of the eccentric masses to each other.
2. Brief Description of the Prior Art
An eccentric mass vibratory machine utilizing concurrently rotating, parallel shafts, each carrying eccentric weights or masses, is disclosed in German Pat. No. 1,015,275. One shaft has a thick gear secured to the shaft for rotation therewith. The second shaft has a pair of discs fixed thereto and spaced longitudinally therealong. The discs carry dogs. A second gear carrying dog-engaging stops on its opposite side faces is rotatably and slidably mounted on the second shaft between the two discs, and meshes with the gear on the first shaft. The stops on the second gear are angularly offset from each other therearound so that, by shifting the second gear axially on the second shaft into engagement with one or the other of the discs, the angular phase relationship of the eccentric masses carried on the shafts is selectively varied.
This arrangement has several disadvantages. The relative angular displacement of the shafts and their eccentrics, and thus the direction of vibrations generated, is effected in steps by repeated reciprocations of the axially shiftable gear on the second shaft. Therefore, the position of the shifting member used to effect a sliding reciprocation of the second gear does not provide an unambiguous and positive indication of the attained angular relationship of the two shafts and their respective eccentric masses.
Furthermore, in the described system it is, as indicated, necessary to axially reciprocate the torque transmitting second gear on the second shaft. In order to accommodate this axial motion of the second gear, the first gear affixed to the first shaft, which is in mesh with the reciprocating gear, must have a width adequate to allow such axial reciprocation. Moreover, the system requires the two described discs with their associated dogs to be located on opposite sides of the axially reciprocated gear. For these reasons, the shifting coupling becomes expensive, and the axial dimensions of the shifting coupling become undesirably large.
An actual, publicly used soil compactor which has been constructed using the general principles of the vibration generating machine described in German Pat. No. 1,015,275 provides for the optional attainment of only two angular positions as between the gear-carrying shafts and their eccentrics. These two angular positions are attained when the axially movable gear is coupled to either one or to the other disc. Therefore, each of the two angular positions corresponds to either a "Forward" or a "Reverse" direction of vibratory movement, and the disadvantage of speculative or ambiguous coupling actions leading to uncertainty in the angular relationship attained, characteristic of the mechanism described in the German patent, is obviated. Whether the system is coupled for "Forward" vibration or "Reverse" vibration will always be known. Nevertheless, this machine, while avoiding the disadvantage of ambiguous coupling and the resulting uncertain angular relationship, continues to possess the remaining disadvantages of the system described in German Pat. No. 1,025,275.
Another type of vibrating machine utilizing counter-rotating shafts and eccentric masses with a shifting coupling is disclosed in German Pat. No. 1,484,588. In this machine, two stops are provided within a housing which is attached to a gear rotatably mounted upon one of the two shafts. The shifting coupling forming a part of the assembly comprises a shifting ring mounted on the same shaft as this gear and housing, and susceptible to axial displacement along the shaft. The ring carries a dog which cooperates with a selected one of the two stops carried on the housing. These stops are angularly spaced around the housing by 180.degree.. When the dog on the shifting ring is engaged with one of the stops, the gear which is carried on the housing is coupled to the shaft. Ramps or inclined surfaces are provided on the shifting ring, and these ramps in turn cooperate with cams carried on the shifting ring.
The shifting ring is actuated by moving it axially along the shaft upon which it is mounted, whereby the dog will be disengaged from one stop. At this time, the driven structure, i.e., the shaft which rotatably carried the gear and its associated housing, along with the eccentric carried on this shaft, will lag in its rotational velocity the drive shaft carrying a fixed gear. As the shifting ring continues its axial movement, the ramps on the end face of the gear are reached and the shifting ring is slightly axially shifted in the reverse direction prior to the time the next stop on the housing overtakes and engages the dog on the ring. This stop is offset angularly by 180.degree. from the stop previously disengaged from the shifting ring.
The vibration machine described in German Pat. No. 1,484,588 also suffers from several disadvantages. The shifting ring is reciprocated axially to and fro with each coupling and uncoupling operation. Such reciprocation increases the wear on the ring and on the shaft upon which it is mounted. Moreover, the design is complex. Further, from outside the housing in which the system is located it is difficult to recognize the particular operative position of the shifting ring, and to immediately verify the status of its engagement with the housing stops. Finally, in the disclosed system the coupling force is transmitted laterally on the coupled gear, and thus imposes undesirable stresses.
German Auslegeschrift or Offenlegungschrift No. 2,008,055 discloses a vibrating machine which utilizes counter-rotating shafts carrying eccentric masses, and having a shifting coupling for changing the phase relationships of the shafts and their masses. Axially spaced stops are provided in a housing which is laterally affixed to a gear which is rotatably mounted on one of the shafts. A radially projecting dog extends from a shifting rod which is guided in the shaft carrying the housing and its associated gear, with such dog extending through a window provided in this shaft. In effecting coupling and decoupling of the shaft to the housing and associated gear, the shifting rod is moved to locate the dog in the plane and path of movement of either one or the other of the stops carried on the housing. With this arrangement, the impact which occurs following disengagement of the coupling, and at the time when the radial dog hits the next stop, acts directly on the shifting mechanism and severely stresses the shifting rod and its associated radial dog.
An object of the present invention is to design a shifting coupling which can be used to couple counter-rotating, eccentric mass-carrying shafts in a selected angular phase relationship, with such coupling designed so that the meshing gears utilized may have equal widths, and the need for axial displacement of one gear relative to another while continuing to mesh therewith can be avoided.
It is also an object to provide a shifting coupling of the type described such that the precise operative position of the coupling, and therefore the status of the counter-rotating shafts and their eccentric masses relative to each other, can easily be seen from outside the system by reference to a coupling actuator member.
Another object of the invention is to prevent the impact forces, developed at the time when an entrainment device forming a portion of the coupling hits a stop means, also forming a portion of the coupling, from being transmitted to the coupling shifting mechanism.
According to the invention, these and additional objects and advantages are achieved by including in the vibrating machine an entrainment device which comprises a lever pivotally mounted on the driven shaft of the system for pivotation about an axis which extends transversely to the axis of rotation of the driven shaft. With such an arrangement, the pivotable lever on the driven shaft is supported against the transmitted torque through the pivot bearings on a relatively long lever arm. These pivot bearings take up the impact forces developed upon engagement of the entrainment device to couple the shafts. The shifting mechanism acts in the plane of pivotal movement of the layer, and is not affected by the impact forces. The gears employed on the two shafts can be axially stationary on their respective shafts, and can have equal widths. Further, it is possible to immediately recognize the particular operative position or status of the coupling and entrainment device from the position of an external portion of the actuator member. The stop utilized for coupling and uncoupling can be provided directly on the driven gear and close to the central plane thereof. The entire arrangement can be made simple and compact.
Additional objects and advantages of the present invention will become apparent as the following detailed description of two preferred embodiments of the invention is read in conjunction with the accompanying drawings which illustrate such embodiments.